/***浏览器兼容
		 * 
		 */
		//URL工具类
		window.URL = window.URL || window.webkitURL || window.mozURL || window.msURL;	
		//多媒体控制器
    	window.navigator.getUserMedia = (navigator.getUserMedia || 
    			navigator.webkitGetUserMedia || 
    			navigator.mozGetUserMedia || 
    			navigator.msGetUserMedia);
    	//PeerConnection,简称pc
    	window.PeerConnection = (window.PeerConnection ||
                window.webkitPeerConnection00 || 
                window.webkitRTCPeerConnection || 
                window.mozRTCPeerConnection);
    	//session描述器
    	window.RTCSessionDescription = (window.mozRTCSessionDescription || window.RTCSessionDescription);
    	//ice候选器
    	window.RTCIceCandidate = (window.mozRTCIceCandidate || window.RTCIceCandidate);
    	var config = {
    			"iceServer" : {
    				iceServers : [  { "url": "turn:122.112.244.131:3478",  
    					  "username": "700",//可选  
    					  "credential": "700pass"//可选  
    					}  ]
    			}
    		};
    	